1. Technical Field
The present invention relates to an additive composition including a counteragent, and more particularly, to an additive composition for preparation of polyolefins, which improve flowability of a nucleating agent and exhibits excellent transparency, by applying a counteragent of a specific structure to a sorbitol nucleating agent which is an additive used in preparation of polyolefins.
2. Description of the Related Art
Generally, polymers are processed and produced so as to exhibit specific properties such as molecular weight, molecular weight distribution, conformation, composition distribution, stereoregularity, crystal structures, amorphous structures, molecular orientation, phase, and the like in order to realize performance and functionality suited to specific applications.
Such properties can be controlled by catalysts, polymerization conditions, polymerization methods and additives, and particularly, nucleating agents serve to control the crystal structure of polymers among such additives. Generally, when nucleating agents are added to polymers, various effects, such as improvement of stiffness, transparency and gloss properties, reduction of a molding cycle, and the like can be obtained. For example, the nucleating agent increases the degree of crystallization of a crystalline resin such as polypropylene during a curing process from a molten state to a solid state, thereby suppressing light scattering while improving transparency and gloss.
Such nucleating agents for polypropylene include AI-PTBBA and sorbitol nucleating agents. Particularly, sorbitol nucleating agents exhibit excellent properties in terms of stiffness and transparency, and thus are widely used.
Such nucleating agents may improve various properties. In this regard, uniform dispersion of a nucleating agent is very important in order to maximize performance thereof. When the nucleating agent is unevenly dispersed, a prepared polymer exhibits significantly deteriorated properties in terms of stiffness, transparency and the like, and a preparation process thereof is not efficient.
Particularly, although sorbitol nucleating agents have been actively developed due to excellent effects thereof, strong adhesion and cohesion of the sorbitol nucleating agents cause a serious problem of non-uniform dispersion thereof during mixing after addition. Moreover, depending upon molding conditions, the nucleating agents are attached to dies, molds, rolls and the like, possibly resulting in product failure.
To solve such problems, although uniaxially oriented polypropylene (OPP) films having excellent transparency are prepared using high melting point polymeric nucleating agents, such as polyvinyl cycloalkane, poly(3-methyl-1-butene), polyalkenyl silane, and the like, the high melting point polymeric nucleating agents provide limited performance when used alone in powder form, and thus cannot function well as a substitute for sorbitol nucleating agents.
Moreover, although complexation of the sorbitol nucleating agent with diverse materials has been studied to solve problems of adhesion and cohesion thereof, existing complexed sorbitol nucleating agents have a serious problem in that transparency of prepared polymers is not secured.
Thus, development of additive compositions capable of solving drawbacks in terms of adhesion and cohesion while improving stiffness and transparency of prepared polymers is an urgent issue.